Traditional techniques for preparing toner include preparing include grinding resin to a fine powder, which is sifted to recover particles of desired size. That process is time consuming and results in a toner product were the particles are not homogenous in shape or size. More recently, emulsion aggregation (EA) methods for producing toner are used. EA techniques may involve a batch or semi-continuous emulsion polymerization, as disclosed in, for example, U.S. Pat. No. 5,853,943, the entire disclosure of which herein is incorporated by reference in entirety. Other examples of EA/coalescing processes are illustrated in U.S. Pat. Nos. 5,902,710; 5,910,387; 5,916,725; 5,919,595; 5,925,488, 5,977,210 and 5,994,020, and U.S. Pub. No. 2008/0107989, the entire disclosure of each of which herein is incorporated by reference in entirety.
Previous one-solvent and two-solvent processes of phase inversion emulsification (PIE) to produce resin particles for making toner are known to produce latex particles of from about 140 to about 230 nm in size (see, e.g., U.S. Pub. Nos. 20110200930 and 20110281215, the entire disclosure of each of which herein is incorporated by reference in entirety), which may not be suitable for effective dispersion of for example, carbon black pigment particles. The organic solvents, for example, methyl ethyl ketone (MEK) and isopropanol (IPA) are used to dissolve the resins to prepare an organic phase containing the dissolved resin and after an optional step of neutralizing resin acid groups by adding a base to the dissolved resin mixture, phase inversion is induced by adding water to produce an oil in Water (O/W) dispersion or emulsion comprising resin particles, and finally, the liquids, that is solvent(s) and water are removed, for reuse in a subsequent PIE reaction, to yield a latex.
Organic solvent(s) and water are removed from a PIE reaction, an organic-rich fraction comprises primarily organic solvent(s) and a smaller amount of any neutralizing agent and water, and a water rich fraction comprises primarily water with smaller amounts of organic solvent(s) and any neutralizing agent. The solvent-rich fragment can be refreshed with neat organic solvent(s) and used to dissolve resin in a subsequent PIE reaction. The water-rich fraction can be used in a subsequent PIE reaction to induce phase inversion.
The PIE process generally is practiced in batch mode, which is time and energy consuming. Attempting to achieve economies of scale for that method is not usually successful because scaling up the process to larger reactors results in a lower surface to volume ratio resulting in greater distillation time to remove the solvent which increases the time and cost of the overall process. A cost effective method of making latex for toner at high yield would be beneficial.